Seeing as Google built the Android platform with the concept of “open” at the forefront of its collective mind, we find the following a bit contrary. It appears as though G1 owners who have taken advantage of haykuro’s handywork and installed the ported version of Android OS 1.5 have now been locked out of the Android Market. In other words, no apps for you. Initially, Google’s app store was working fine for the savvy few who had grown tired of waiting for Google to finally issue the update Android users have been waiting for since last year. As more people caught on and began installing the cooked up Cupcake build, it looks like the Android team has decided to cut off Market access in an attempt to deter people from getting their Cupcake on. Here’s the theory, as stated by xda-developers forum member AndroidAutobot:

Someone said somethin about a Magic being detected in the states and someone having a negative reaction to that being that it hasn’t officially been released in the states. May be some measure Google is taking to prevent Magic use in the states prior to its official release (on the assumption that G builds are somehow registering as Magics w/ the Market). this seems like the most logical theory to me at this point. Which means we’ll all eventually be able to use the G builds again… once the magic has been released in the states if this theory is correct.

Though nothing has been confirmed at this point, it certainly makes sense. The discussion goes on but if you’re a fan of the Android Market is looks like you’ve got a choice to make before upgrading with haykuro’s Cupcake: sit tight for a while longer while Google finishes up development on 1.5 and finally pushes it out, or forgo Android Market access and start enjoying stereo Bluetooth, virtual keyboards, an improved browser and plenty more.

UPDATE: A clarification from the tipster posted in the comments section below (looks like you can still have your Cupcake and eat it, too — for the time being):

I want to clarify that this is currently only affecting one of the two haykuro cupcake builds. The “G” aka “google-sourced” line. There is a second “H” aka “HTC-sourced” line that is currently unaffected by this Market change. So if you get the “H” build, you’ll still have market access. For Now.